Big Block 396 or 402?
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Instructor
Joined: Sep 2020
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Big Block 396 or 402?
I have been helping an elderly neighbor cleaning up some things and next to a now falling apart 69 Corvette which she will not sell was an engine covered and wrapped in a tarp. It seems like it is still in solid shape. I really want to put it in my 76 Corvette if she will sell it. I want to offer a far price even if there is something wrong with it but I do not know what it is the heads are 3964291 and the engine code is 3969854. She said at one point her son had 69 chevelle or camaro SS but backed it into a tree and she thinks the motor came out of it.
How do you know if it is a 402 or a 396 and how do you tell if it is 4 bolt or 2. I looked up the numbers but it could be either. Any help would be great I would like to rebuild it if it is worth it.
How do you know if it is a 402 or a 396 and how do you tell if it is 4 bolt or 2. I looked up the numbers but it could be either. Any help would be great I would like to rebuild it if it is worth it.
Race Director
Joined: Mar 2017
Posts: 11,953
Likes: 4,508
From: Virginia
Why? It's lower displacement than any big block that ever came in a C3, so it will add weight, heat, and volume to your engine bay without any tangible benefit over either a (more) correct big block, or a well-built SBC.
That said, the clue to decyphering the block may be on the engine stamp pad. Look for the two or three letter suffix, and look it up at the link below. That engine may be worth a lot more to someone with a Camaro or Chevelle, perhaps enough to change her mind on the 69 Corvette.
https://nastyz28.com/chevy-engine-code-stampings.php
EDIT: @MelWff types faster.
That said, the clue to decyphering the block may be on the engine stamp pad. Look for the two or three letter suffix, and look it up at the link below. That engine may be worth a lot more to someone with a Camaro or Chevelle, perhaps enough to change her mind on the 69 Corvette.
https://nastyz28.com/chevy-engine-code-stampings.php
EDIT: @MelWff types faster.
Last edited by Bikespace; Aug 3, 2021 at 11:10 PM.
Dr. Detroit
Joined: Mar 2012
Posts: 10,097
Likes: 4,027
From: New Braunfels Texas
Only way to tell two or four bolt is to pull the pan or boroscope it.......but it is a moot point as I have seen Mark IV 2 bolt blocks make 900 horsepower on spray....
396 or 402 is a moot point too.....the 402 is just a .030 over 396.....
The heads are the interesting part as they are Rec port closed chamber head......which means it could possibly be an L-78 396.....Possibly. Remember this **** is 50 years old and anything could have happened....
Find the stamp pad code as suggested.....
You need to gauge the condition of it too....does it turn over, is it crusty...etc.....
The 396 is a great engine.....but with Rec port heads, they are kind of a turd to drive around...the rec port heads do not respond until about 4500rpm....
Jebby
396 or 402 is a moot point too.....the 402 is just a .030 over 396.....
The heads are the interesting part as they are Rec port closed chamber head......which means it could possibly be an L-78 396.....Possibly. Remember this **** is 50 years old and anything could have happened....
Find the stamp pad code as suggested.....
You need to gauge the condition of it too....does it turn over, is it crusty...etc.....
The 396 is a great engine.....but with Rec port heads, they are kind of a turd to drive around...the rec port heads do not respond until about 4500rpm....
Jebby
Team Owner
Joined: Apr 1999
Posts: 21,953
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From: Reno Nevada
2024 C3 of the Year Finalist- Modified
Don't quote me on what is says on the side of the 396 block. But Years ago I had two on pallets. In bold letters it said "high Performance" on the side of the block. When I pulled the heads off to see what was inside they were the high compression with the notched out cylinder bore to clear the big intake valves. By casting number mine were the Z-16 for chevelles 11:1 C/R and 375 hp.
As to value..... cubic inches rule and even 427's aren't that desirable. Bib block parts cost more than a small block. But in the past we used them for all kind of hot rodding projects. BBC is so much more durable than a small block when you get into higher hp. My friend has a 69 Camaro 396 with a 250 shot that is something over 700 RWHP. You really can't do that with a small block
As to value..... cubic inches rule and even 427's aren't that desirable. Bib block parts cost more than a small block. But in the past we used them for all kind of hot rodding projects. BBC is so much more durable than a small block when you get into higher hp. My friend has a 69 Camaro 396 with a 250 shot that is something over 700 RWHP. You really can't do that with a small block
Pro
Joined: Jan 2016
Posts: 502
Likes: 103
From: Reno Nevada
FWIW, certain most and I am pretty sure all big blocks have the "high performance" casting in the block. The value for this block is going to be to a Chevelle or Camaro owner. Both cars came with this block and many of these owners are after this block. Depending on the actual casting, it could be worth something, but likely not a lot. As far as putting it in your Corvette, it will work fine and can be a good running engine. I would probably stick to a 454 or larger though for probably the same price. You can get many brands of bare big blocks over the counter brand new ready to build or there are plenty used for sale if you look around.
Dr. Detroit
Joined: Mar 2012
Posts: 10,097
Likes: 4,027
From: New Braunfels Texas
As to value..... cubic inches rule and even 427's aren't that desirable. Bib block parts cost more than a small block. But in the past we used them for all kind of hot rodding projects. BBC is so much more durable than a small block when you get into higher hp. My friend has a 69 Camaro 396 with a 250 shot that is something over 700 RWHP. You really can't do that with a small block
The only way a 396/402 is viable to build now is if you find a good running wore out core......the oval 325/350hp ones are the ones to have.....bore, hone, pistons, rings, cam, intake and some home porting will yield one a solid 450 horse pounder for dirt cheap.......building one from scratch is not a smart move as the 454 block has a bigger bore and is just as expensive to build from scratch.
Jebby
Is my vette stock?? HAHA
Joined: Oct 2015
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From: Im not allowed to tell you
2020 C3 of the Year Finalist - Modified
2020 Corvette of the Year Finalist (performance mods)
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The only down side is that if you keep the bore small like the 396/402, finding cheap aluminum heads isnt possible. The newer heads need atleast the 4.125 bore for the valve clearance unless you do some valve clearancing in the top of the bore. If you buy some high end heads like ASFR or Brodix you can find heads for the 396....Other than that the 396 will bolt right in and you can use anything you want for BBC parts. If you want to build it into a 427 its just boring and using the bigger piston, its the same crank. Im planning on building a 454 block I have into a 427 and the 402 block I have will either be sold as is or built into a 427 as well. With the stock rearend, my 5 speed and where I am in life, I just want a 500hp/ 500 ftlbs engine....I dont need 600 plus horse anymore. I had losts of fun with the 450hp 327 I built but it lost a lifter and the head gasket went so it needs some major machining in the future.
As for performance, if you have the 10.5:1 domed pistons and put in a good cam, I have .540/.540 cam, ( the .520/.540 retro cam i wanted was'nt available until sept), its a fun motor
As for performance, if you have the 10.5:1 domed pistons and put in a good cam, I have .540/.540 cam, ( the .520/.540 retro cam i wanted was'nt available until sept), its a fun motor
Last edited by Rescue Rogers; Aug 4, 2021 at 03:45 PM.
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Is my vette stock?? HAHA
Joined: Oct 2015
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From: Im not allowed to tell you
2020 C3 of the Year Finalist - Modified
2020 Corvette of the Year Finalist (performance mods)
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2016 C3 of Year Finalist
See if you can spin it over. I would offer her anywhere from $500 to $1000. If it has the intake, exhaust manifolds and carb, offer $1000, its up to you. I got a decent setup for $900 and replaced everything bearing and ring wise since it was an unknown. Upraded the connecting rod studs to ARPs. I ried running the Sniper on it but she didnt like it with the Gm dual plane.
My valve seals were upgraded to Viton seals by the PO and needed replacing but I couldnt get any due to covid...not a huge deal, its the only thing I couldnt get in a short period so I could get it on the road. I've got oval port 98cc heads and a 68 oval port tri power on mine. Other than fine tuning the center carb for idle to cruise transition its awesome. Im getting 11.5 mpg with the 4 speed doing city driving with a 4.11 rear end.
My valve seals were upgraded to Viton seals by the PO and needed replacing but I couldnt get any due to covid...not a huge deal, its the only thing I couldnt get in a short period so I could get it on the road. I've got oval port 98cc heads and a 68 oval port tri power on mine. Other than fine tuning the center carb for idle to cruise transition its awesome. Im getting 11.5 mpg with the 4 speed doing city driving with a 4.11 rear end.
Is my vette stock?? HAHA
Joined: Oct 2015
Posts: 20,216
Likes: 9,354
From: Im not allowed to tell you
2020 C3 of the Year Finalist - Modified
2020 Corvette of the Year Finalist (performance mods)
2019 C3 of Year Winner (performance mods)
2016 C3 of Year Finalist
I had my cam numbers backwards........bit bigger but still not huge by todays standards
Burning Brakes
Joined: Nov 2012
Posts: 788
Likes: 100
From: Indianapolis IN
3969854 is a '69 396 or a '70 - '72 402, have you transposed the 5 & 4 ? Look at the lifters since the manifold is off to see if they're solids, it could be a genuine 375HP engine that's valuable to someone.( but I'd much rather start with a 454 block if not doing a restoration)
Safety Car
Joined: Nov 2008
Posts: 3,720
Likes: 554
From: Seattle Washington
The Valve Spring retainers are not Original. It looks like the inside of the Square Port Heads have been painted with Gyptal paint. All very common late 70's early 80's Performance mods. If You can not find a Serial Number on the Head surface this means the Block has been Decked. So what does this tell Us. The sky is the limit. We know somebody has been inside there before Us, so we have no idea what Pistons, Rods, Crank or Cam lye below. The only way to find out is to take it apart. If I was looking to buy it I would be using a Bore Scope threw the Plug Holes. If You see shinny Cylinder Bores and Domed Pistons then things are looking up. If You see Flat Pistons with 4 Valve reliefs and a Rust Spot at the out side of the bore where it meets the Piston Top then You might be looking at scrap. All it takes is one Teaspoon of water to get in there and you have a Rust spot in any Cylinder and it will probably will not clean up with .030 overbore. If the Block has been Decked then You can figure it has also been bored .030 already. . However I think 396's have a lot of meat in them to bore.
Safety Car
Joined: Nov 2008
Posts: 3,720
Likes: 554
From: Seattle Washington
I'm Seeing Gyptal Paint inside the lifter valley as well. This Engine has spent some quality time in a Machine Shop. Who knows what expensive High Performance parts lurk with in. Bu Oh No some of the Valve Tips are Rusted ! This means its been stored in a Rust environment. Use due caution and expect the worst.
Safety Car
Joined: Nov 2008
Posts: 3,720
Likes: 554
From: Seattle Washington
So I missed the picture with the Serial Number so it would appear that the Block has not been Decked. And it also looks as though the out side of the Engine was never painted ?? If so it could mean the Engine was never installed in a car after leaving the Machine Shop. I'm a bit concerned that the Push Rod Guides are Painted with Gyptal. What Machine Shop wouldn't bother to remove them before painting ? Maybe the painting wasn't done in a machine shop at all and done under a shady tree.
Pro
Joined: Jul 2021
Posts: 719
Likes: 156
Nice numbers or not .... It's been into, so anybody's guess what's inside. It may be sugar or scrap sh7t. If she's a respected elder, ya won't want any short or long term ill will. If me, be perfectly willing to courteously walk away when offering $300 plus taking care of any cleanup etc of her storage area.
Remember that ol' bromide: ya don't shyt where ya eat.
Remember that ol' bromide: ya don't shyt where ya eat.
Safety Car
Joined: Nov 2008
Posts: 3,720
Likes: 554
From: Seattle Washington
Yikes, even the Valve Springs have Paint on them along with the Aluminum Spring Retainers. I'm changing my tune from spending some quality time in a machine shop getting Gyptal Paint to spending some time under a shade tree getting a Rustoleum Rebuild.